It's a passive exotic so it shouldn't be all that powerful, but it shouldn't suck like it does. It really doesn't feel like it gives you much energy back for getting hit and the "full health when critical" just means it gives you the health and no shields, so you are still stuck at pretty much one shot range in pve if you do any particularly challenging activity or by anything in PvP. I think it granting full health like it does currently, but some shield as well might make it useful. Like maybe 20% shields. I have no idea how much energy you get back for getting hurt but it really doesnt feel like you are getting much for how much health you lose. It also feels like it has a cool down too. Maybe make it increment based where you just get a flat amount of cool down? Lose 20% of your total health+shields? Gain like 12.5% energy for abilities. Please buff it.